How does dynamic dispatch work

Type System
2026-04-17T12:05:42+00:00
Dynamic dispatch uses the `dyn` keyword and trait objects to resolve method calls at runtime instead of compile time.

Dynamic dispatch in Rust works by using the dyn keyword to create a trait object that defers method resolution until runtime. Instead of the compiler knowing the exact type at compile time, it generates a virtual method table (vtable) for the trait, allowing the program to call the correct implementation based on the actual type of the value stored in the pointer.

trait Draw {
    fn draw(&self);
}

struct Button;
impl Draw for Button {
    fn draw(&self) { println!("Drawing a button"); }
}

fn main() {
    let button = Button;
    let trait_obj: &dyn Draw = &button;
    trait_obj.draw(); // Calls Button's draw at runtime
}